1. Field of the Invention
The present invention relates to eyewear, and more particularly, to corrective eyewear that provides the option of using a lens or a pinhole aperture disposed adjacent to the lens.
2. Description of Related Art
There are a number of conditions of the eye that affect one's visual acuity over a range of distances. Myopia (“near-sightedness”) refers generally to a condition in which distant objects appear blurred. It is often caused by an elongated eyeball which causes light to focus in front of the retina instead of directly on it. On the other hand, hyperopia (“far-sightedness”) refers to the opposite condition, in which nearby objects appear blurred. As one might guess, hyperopia is caused by a shortened eyeball which causes light to focus behind the retina instead of directly on it.
Those who are fortunate enough to have avoided developing myopia or hyperopia, however, will inevitably develop presbyopia. Presbyopia is a vision condition in which the crystalline lens of the eye loses its flexibility, making it difficult to focus on close objects. Presbyopia usually becomes noticeable in the early to mid-40s and is a natural part of the aging process of the eye. It is not a disease, and it cannot be prevented. Thus, the need for corrective eyewear will be inevitable for most people.
The most common types of corrective eyewear are corrective lenses, such as glasses or contact lenses. Corrective lenses may be worn to correct most refraction errors of the eyes. Single vision lenses have the same optical correction over the entire area of the lens and are therefore suitable for those who suffer from a single refractive error. Many people, however, may suffer from more than one refractive error. For example, a person may have various combinations of myopia, hyperopia, presbyopia, or astigmatism. In such cases, bifocals, trifocals, or progressive lenses may be necessary.
Bifocals and trifocals are eyeglasses in which the lenses have two and three distinct regions of different optical powers, respectively. Bifocals are most commonly prescribed to people with presbyopia who also require correction for myopia, hyperopia, and/or astigmatism. Trifocals similar to bifocals, with the exception that trifocals have an additional segment for intermediate vision above the reading section and below the distance section. Trifocals are becoming rarer as more and more people are choosing to wear progressive lenses. Progressive lenses provide a gradient of increasing lens power, from minimal or no magnification at the top of the lens to maximum magnification at the bottom of the lens. A wearer can view objects at different viewing distances by directing his line of sight through appropriate parts of the lens.
Although corrective lenses have been developed to correct a variety of refractive errors, they are still limited to correcting predefined refractive errors in a person's eyes. Thus, once prescribed and cut, corrective lenses are not adjustable to further other changes in a person's vision. An additional eye examination will be necessary to address these changes in the person's vision. What is needed therefore is an optical device which, in addition to corrective lenses, can easily provide yet another way for improving one's visual acuity over a range of distances.